Graphene oxide-assisted Au nanoparticle strip biosensor based on GR-5 DNAzyme for rapid lead ion detection.

This study has reported that a GR-5 DNAzyme based lead ion strip biosensor could exhibit an enhanced specificity with the assistance of graphene oxide (GO). This enhancement results from the specific π-stacking interaction between the ribose rings of the nucleobases and the carbon hexagons in GO which can reduce the false positive interference by removing unhybridized ssDNA during the annealing of GR-5 DNAzyme. Meanwhile, conjugate pad was sprayed with two kinds of AuNP-DNA probes, and nitrocellulose membrane test zone and control zone were immobilized with two kinds of biotin-DNA probes, respectively. The limit of detection of this strip biosensor was estimated to be about 0.05 nM (S/N = 3) and 1 nM (with naked eyes) with a linear range from 0.01 to 100 µM. Furthermore, the strip biosensor exhibited excellent selectivity toward Pb2+ in the presence of other divalent metal ions. For real soil samples, the obtained recoveries were in the range from 91.5% to 113.1%.